Download sustainable desalination: environmental

SUSTAINABLE DESALINATION: ENVIRONMENTAL APPROACHES
Authors:
F. Lokiec
Presenter:
Fredi Lokiec
Executive Vice President, Special Projects – IDE Technologies Ltd. – Israel
[email protected]
Abstract
The environmental issues of possible concern during construction and operation of desalination plants
(mainly large-scale facilities) include impacts that are common to many coastal development projects
(e.g. land use and aesthetic impacts), as well as specific impacts associated with the elements of the
desalination system and auxiliary infrastructure. In the latter category these relate to the introduction of
highly saline brine and process additives to the marine environment, and to the emission of greenhouse
gases and air pollutants due to the energy demand of the desalination process. Other environmental
issues of possible concern must be considered, such as entrainment and impingement of marine
organisms from the intake of seawater, hazards associated with storage and use of various chemicals,
noise, etc. Most of the potential environmental impacts during construction and operation of desalination
facilities are of a local nature. The potential environmental impacts during operation are mostly
continuous, while those associated with construction activities are temporary and mostly reversible.
IDE strives to conduct its business with responsibility towards the environment and promotes the use of
environmentally friendly technologies and approaches, avoiding or mitigating potential environmental
impacts. The specific mitigation measures represent the ‘state-of-the-art’ with respect to environmental
management of desalination facilities and ensure compliance with applicable environmental legislation.
This paper assesses the potential environmental impacts on the marine and terrestrial environments, as
well as on the atmosphere, at both construction and operation stages of large-scale desalination facilities,
and describes the solutions implemented at IDE’s largest and most modern facility in Sorek (150M m3/y
– 624,000 m3/d), which have been classified as the “best available technology”, on the management of
the potential environmental impacts.
Field experience results of several monitoring programs on the marine environment in the proximity of
large scale desalt plants in Israel and Australia is also assessed.
The International Desalination Association World Congress on Desalination and Water Reuse 2013 / Tianjin, China
REF: IDAWC/TIAN13-012
I.
INTRODUCTION
Global depletion of water sources and water scarcity are serious problems that are affecting municipal
health and industry in an increasing number of regions throughout the world. In many countries the lack
of water resources also acts as a limiting factor affecting the development and growth of their economic
sectors, thus affecting countries’ GDP.
As seawater desalination technologies have matured over the past four decades, seawater desalination is
being increasingly utilized by both governmental agencies and industry as a sustainable solution to the
lack of usable water.
While the social and economic benefits of desalination are recognized, scientific and public concerns are
raised over potential adverse impacts of desalination on the environment. Key concerns are the energy
demand to drive the process and the emission of greenhouse gases. Impacts associated with land use,
construction activities, intake and the related effects of concentrate discharge are also among the main
issues raising public awareness.
The desalination industry is focused today on incorporating sustainability aspects and mitigation
measures into the design and operation of desalination plants, rising to the challenge to reduce the
environmental footprint of desalination facilities and recognizing effective environmental management
that also brings potential economic benefits.
The potential environmental impacts on the marine and terrestrial environments, as well as on the
atmosphere, at both construction and operation stages of large-scale desalination facilities are analyzed
in this paper, which also describes various measures and approaches aimed at avoiding, mitigating or
minimizing these potential environmental impacts. Field experience results of several monitoring
programs held on the marine environment in the proximity of large scale desalt plants in Israel and
Australia is also assessed.
II.
ENVIRONMENTAL ISSUES OF POSSIBLE CONCERN
The environmental issues of possible concern (potential environmental impacts) during construction and
operation of SWRO facilities include impacts that are common to many coastal development projects
(e.g. land use and aesthetic impacts), as well as specific impacts associated with the elements of the
desalination system and the auxiliary infrastructure. The main issues of possible concern in the latter
category are related to the introduction of highly saline brine and process additives to the marine
environment, and to the emission of greenhouse gases and air pollutants due to the energy demand of the
desalination process. In addition, various other environmental issues of possible concern must be
considered, such as entrainment and impingement of marine organisms from the intake of seawater,
hazards associated with storage and use of various chemicals and more. Most of the potential
environmental impacts during construction and operation of SWRO facilities are of a local nature. The
potential environmental impacts during operation are mostly continuous, while those associated with
construction activities are mostly temporary and reversible.
The potential environmental impacts of a desalt plant during the construction and operation stages are
presented in Tables 1, 2 and 3 below.
The International Desalination Association (IDA)
World Congress on Desalination and Water Reuse
REF: IDAWC/TIAN13-012
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The Tables include estimates of the spatial extent of each potential environmental impact under the
assumption that no impact mitigation measures have been adopted. This classification, based on the
evaluation in UNEP (2008), gives an indication of the significance of each impact and consequently of
the significance of the planned mitigation measures presented in Section ‎III. The spatial scales are
defined as follows:
Localized
Mid-range
Far range
=
=
=
punctual, within the area of the project site, within 100m of origin;
within the project site and nearby areas, within 1,000m of origin;
effects beyond project site and nearby areas, beyond 1,000m of origin.
Table 1: Potential Environmental Impacts - Construction Stage
Potential Environmental Impact
Impact
Location
Spatial extent
Alteration of the natural terrain
Onshore
localized
Impacts of construction wastes and
excess soil
Soil and groundwater pollution (fuels,
oils, etc.)
Air pollution (fugitive dust emission)
Onshore &
Offshore
Onshore
localized
Onshore
mid-range
Noise emission
Onshore
mid-range
Damage to antiquities
Onshore &
Offshore
Offshore
Offshore
localized
Alteration of the seabed
Sediment resuspension (impacts on
marine water quality and ecology)
Oil pollution
Offshore
localized
localized
localized to midrange
localized to far-range
Source of impact
Earth works,
construction works
Earth works,
construction works
Earth works,
construction works
Earth works,
construction works
Earth works,
construction works
Earth works,
construction works
Marine works
Marine works
Marine works
Table 2: Operation Stage –Potential Impacts on the Marine Environment
Potential Environmental Impact
Impact
Spatial extent
Source in the Facility
Habitat alteration and changes in sediment localized
Intake & outfall systems (piping)
transport
Entrainment and impingement of marine
localized to mid-range Intake system (suction heads)
biota
Debris pollution (from intake screening)
localized
Intake system (screening system)
Biological effects of residual chlorine &
localized to mid-range Intake system (biofouling control)
chlorination by-products
Biological effects of increased seawater
localized to midConcentrate outfall (RO brine)
1
salinity
range
1
Refers to > 5% salinity change compared to ambient salinity.
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REF: IDAWC/TIAN13-012
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Potential Environmental Impact
Impact
Spatial extent
Source in the Facility
Effects of residual chemicals (ironlocalized to mid-range Concentrate outfall (process
hydroxide, metals, antiscalants, membrane
streams)
cleaning chemicals) and particulate matter
in the concentrate2 (biological & aesthetic
impacts)
Table 3: Operation Stage – Potential impacts on the terrestrial environment and atmosphere
Potential Environmental Impact
Impact
Spatial extent
Source in the Facility
Alteration of the coastal environment and
Localized
Onshore pipelines and pumping
obstruction of free passage along the
station
seashore
Emission of greenhouse gases and air
Mid- to far-range
Power generation
pollutants
Noise emission
Mid- to far-range
Pumping station and main plant
Light “pollution”
Localized
Main plant
Accidental spillage or leakage of
Localized to midMain plant (storage & handling of
hazardous chemicals
range
chemicals)
Solid waste and sanitary sewage
Localized
Main plant (used containers,
maintenance works wastes, office
wastes, sanitary sewage)
Aesthetic impacts (landscape and natural
Localized to midAll inland structures
scenery)
range
III.
ENVIRONMENTAL MITIGATION MEASURES
3.1.
Overview
IDE’s mitigation measures aimed at avoiding or minimizing the potential environmental impacts in its
mega-size projects are tailored according to each site and its boundary conditions. This section presents
the solutions implemented at IDE’s largest and most modern facility in Sorek (150M m3/y –
624,000 m3/d), which have been classified “state-of-the-art” and constitute the “best available
technology” on the management of the potential environmental impacts listed in the previous section.
The environmental mitigation principles underpinning the specific mitigation measures adopted in the
design, construction and operation of IDE’s Sorek mega-plant include employment of environmentallyfriendly construction methods; rehabilitation of areas affected during construction, and; design assuring
minimal alteration of the natural environment, minimal energy consumption and minimal use and
discharge of process chemicals. The specific mitigation measure depicted for each impact ensures
compliance with the requirements of the applicable environmental legislation.
2
In this document “concentrate” means the RO brine and the process streams discharged to the sea with the brine.
The International Desalination Association (IDA)
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REF: IDAWC/TIAN13-012
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Routine environmental monitoring, as applicable in IDE’s large-scale desalination facilities, is
envisaged to be applied in Sorek in order to verify the impact assessments associated with the operation
of the facility and to trigger additional mitigation efforts if necessary.
3.2.
Mitigation Measures - Construction Stage
Table 4 presents mitigation measures adopted for avoiding or minimizing environmental impacts during
construction of the Sorek facility. Following the table, a succinct description of the most significant
mitigation measures is provided.
Table 4: Construction Stage - Mitigation of Potential Environmental Impacts
Potential Environmental Impact
Impact
Alteration of the natural
terrain (land area)
Impacts of construction
wastes and excess soil
Soil and groundwater
pollution (fuels, oils,
etc.)
Air pollution (fugitive
dust emission)
Noise emission
Damage to antiquities
Alteration of the seabed
Mitigation Measures
Source of impact
Earth and
Pipe-jacking (tunnelling) for
construction works installation of onshore pipelines
(seawater feed and brine)
Rehabilitation of grounds used as
temporary organization areas during
construction
Measures for soil retention in plant
area
Earth and
Recycling of construction wastes and
construction works use or authorized dumping of excess
soil
Earth and
Placement of fuel/oil tanks in
construction works containment basins; special care during
fuelling operations; collection and
proper disposal of used lubricating oils
Earth and
Surface wetting; covering of loaded
construction works trucks exiting work areas
Earth and
Limits on working hours and on noise
construction works emission from construction equipment
as required by law
Earth and marine
Actions as prescribed by Antiquities
works
Authorities
Marine works
Pipe-jacking for installation of offshore
pipelines (intake & outfall) to at least
600m from the shoreline; precisely
controlled dredging for installation of
pipelines from 600m; covering of the
pipelines and restoration of the original
bathymetry
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REF: IDAWC/TIAN13-012
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Section in
this
document
3.2.1
3.2.2
3.2.3
-
3.2.4
3.2.1
Potential Environmental Impact
Impact
Sediment resuspension
Oil Pollution
Source of impact
Marine works
Marine works
Mitigation Measures
Minimal dredging activities;
minimization of drifting and sweeping
of dredger suction head by precise
positioning control
Prevention of oil pollution from vessels
Section in
this
document
3.2.1
-
3.2.1 Installation of offshore and onshore pipelines by pipe-jacking and limited, precisely controlled
dredging at sea - Offshore intake and outfall pipelines, within the breaker zone and to a distance of at
least 600m from the shoreline, and the onshore connecting pipelines to the pumping station are installed
by pipe-jacking, a well proven tunnelling method for the installation of underground pipelines. This
method, illustrated in Figure 1, avoids the environmental problems commonly associated with traditional
open cut trenching. Specifically, use of this method does not cause any alteration of the natural coastal
terrain; avoids disruption of coastal ecosystems; saves the need for erecting a cofferdam at the beach,
and minimizes disturbance of the marine environment, including sediment resuspension. The dredged
material is stored at an authorized site at sea and, upon completion of the pipeline installation, is used for
covering the pipes (backfill) and restoration of the original bathymetry.
Spoils from the pipe-jacking process, removed through the start pits, is managed as follows: marine
material is returned to the sea subject to authorization and in accordance with applicable law; terrestrial
material is either dumped at sea (if found suitable) subject to authorization, or used as material for
batteries around Facility site. Upon completion of the pipe-jacking works, the onshore start pit is
covered with a roof 1m below the natural soil level, and the entire area is restored to its original state.
Figure 1: Illustration of Pipe-Jacking Method
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3.2.2. Rehabilitation of grounds used as temporary organization areas - Temporary organization areas
during construction include areas for temporary office, storage, logistics and a special area allocated for
various forms of construction waste. Upon completion of the construction works, all temporary
organization areas are rehabilitated: the areas are cleared (buildings and materials dismantled and
removed), the compact aggregates and concrete wastes are recycled (Section 3.2.3 below), and the
original topography is restored as feasible.
3.2.3. Recycling of construction wastes and use of excess soil - Waste materials from construction of
the facility are recycled. Compact aggregates from temporary organization areas are reused for the first
layer under the roads of the site. Concrete wastes and stones are crushed and recycled to be used as the
under-layer of the site’s roads. Steel is collected and removed from the site to be recycled. Plastic and
wood are removed and recycled off-site. Excess and leftover soil from digging and piping works is used
for leveling the site to the desired elevation, and can also be used as material for batteries around the
site.
3.2.4. Prevention of damage to antiquities - Actions to preserve and prevent damage to antiquities
during the construction stage are as prescribed by the local competent Antiquities Authority (“the
Authority”). Since parts of the areas designated for the plant and associated infrastructure facilities were
“Declared Antiquities Sites”, a preliminary antiquities survey was conducted and findings were properly
removed. Furthermore: (a) all earthworks were carried out in the presence of an inspector representing
the Authority and according to the inspector’s instructions regarding preservation and prevention of
damage to antiquities; (b) in the event of antiquities discovered on land or at sea, actions were
coordinated with the Authority.
3.3.
Mitigation measures - Operation Stage
Table 5 and Table 6 present the mitigation measures incorporated in the Sorek plant design for avoiding
or minimizing environmental impacts during operation. Following the tables, a succinct description of
the most significant mitigation measures is provided.
Table 5: Operation Stage - Mitigation of potential environmental impacts on the marine
environment
Potential Environmental Impact
Impact
Source of impact
Marine habitat alteration and
changes in sediment transport
Entrainment and impingement
of marine biota
Debris pollution
Biological effects of residual
chlorine & chlorination byproducts
Mitigation measures
Intake & outfall
systems (piping)
Intake system
(suction heads)
Intake system
(screening system)
Intake and outfall pipelines laid
below the seabed
Intake heads designed for slow
suction velocity
Self-cleaning traveling screen for
debris collection; disposal of
collected debris in authorized
waste disposal sites
Intake system
Chlorine dosing (shock treatment)
(biofouling control) into the intake in the direction of
the plant, avoiding chlorine
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REF: IDAWC/TIAN13-012
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Section in
this
document
3.3.1
3.3.3
3.3.4
-
Potential Environmental Impact
Impact
Source of impact
Biological effects of increased Concentrate outfall
seawater salinity
(RO brine)
Effects of residual chemicals
(iron-hydroxide, metals,
antiscalants, membrane
cleaning chemicals) and
particulate matter in the
concentrate (biological &
aesthetic impacts)
Concentrate outfall
(process streams)
Mitigation measures
discharge to the sea
Outfall diffuser system designed to
enhance initial dilution of
concentrate
Minimal use of chemicals (process
additives)
Land-based treatment of dualmedia filter backwash prior to
discharge and disposal of the
sludge in authorized waste
disposal sites
Use of environmentally harmless
antiscalants
Treatment of limestone reactors
washings together with dual-media
filters backwash
Use of inorganic solutions only for
membrane cleaning and
neutralization of cleaning
solutions prior to discharge
Section in
this
document
3.3.5
3.3.6
3.3.7
3.3.8
3.3.9
3.3.10
Table 6: Operation Stage - Mitigation of potential environmental impacts on the atmosphere and
land area
Potential Environmental Impact
Impact
Alteration of the coastal
environment and obstruction
of free passage along the
seashore
Emissions of greenhouse
gases and air pollutants
Noise emission
Light “pollution”
Source of impact
Onshore pipes and
pumping station
Power generation
Pumping station and
main plant
Main plant
Mitigation measures
Interconnecting pipelines (intake &
outfall) laid underground; pumping
station located inland at plant site
Minimal energy consumption;
power plant fuelled by natural gas as
the main source of energy; capture
of CO2 from gas burning and its use
during the post – treatment stage
Acoustic insulation of the Facility
structures
Minimal external lighting; minimal
light “spillage” onto areas beyond
Facility site
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REF: IDAWC/TIAN13-012
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Section in
this
document
3.3.2
3.3.11
3.3.12
-
Potential Environmental Impact
Impact
Accidental spillage or
leakage of hazardous
chemicals
Solid waste and sanitary
sewage
Aesthetic impacts (landscape
and natural scenery)
Source of impact
Main plant (storage
& handling of
chemicals)
Main plant
operations
All inland structures
Mitigation measures
Safety measures for transportation,
storage and handling of chemicals as
prescribed in applicable legislation;
placement of storage tanks for
corrosive chemicals in secondary
basins; chemical neutralization of
any spill prior to disposal
Waste segregation; containers for
solid waste collection; waste
disposal in authorized sanitary
landfills; waste recycling as feasible;
proper disposal of sanitary sewage
Architectural
Section in
this
document
3.3.13
3.3.14
3.3.15
3.3.1 Laying of offshore intake and outfall pipelines below the seabed - Laying the intake and outfall
pipelines below the seabed avoids all environmental impacts that may occur if the pipelines were to be
placed on the seabed (i.e. creation of artificial hard-substrate habitats; changes in sediment transport
patterns and erosion phenomena)3.
3.3.2. Laying of onshore pipelines underground and location of pumping station far from the shoreline
- Laying the on-shore interconnection pipelines (seawater and brine) underground, and location of the
pumping station at the main plant site 2.2 km away from the shoreline, prevents any permanent
alteration of the coastal environment and any obstruction of free passage along the seashore.
3.3.3. Intake suction heads designed to minimize entrainment and impingement effects - In order to
minimize entrainment and impingement of biota from the intake of seawater4, the design of the intake
suction heads assures a slow suction velocity of 0.15 m/sec, comparable to normal ambient sea currents.
Such velocity is slow enough to allow virtually all mobile organisms (e.g. fish, large crustaceans) to
swim away from the intake and avoid impingement, as well as to minimize the potential for entrainment
of drifting small biota (plankton, fish eggs, larvae)5. Therefore, significant ecological losses to source
populations of the entrained/impinged species are not expected.
3.3.4. Collection and disposal of marine debris - Self-cleaning traveling screens are installed at the
intake pit to eliminate debris. The removed debris is collected into dedicated containers for eventual
disposal in authorized waste disposal sites.
3
The intake heads and outfall diffusers which are located above the seabed are not expected to influence sediment transport.
Entrainment occurs when intake pipes take in small aquatic organisms, including plankton, fish eggs, and larvae, with the
intake water. Impingement is the pinning and trapping of fish or other larger organisms against the screens of the intake
structures.
5
The US Environmental Protection Agency recognizes reduction of intake flow velocity to 0.152 m/sec (0.5 feet/sec) or less,
as Best Technology Available for impingement reduction.
4
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3.3.5 Outfall designed to enhance initial dilution of concentrate - In order to minimize the spatial
extent of the area affected by the concentrate discharge (salinity and residual chemicals), a specially
designed diffuser has been installed at the outlet of the concentrate outfall. The detailed design, aimed to
enhance rapid initial dilution of the concentrate, takes into account the local hydrographical and
meteorological conditions, as well as the results of Far and Near Fields Marine Dispersion Models.
3.3.6 Minimal use of chemicals - The use of chemicals in reverse osmosis desalination plays a main
role in the membrane separation process, especially when low Boron concentration is required. In Sorek,
the types of chemicals used are restricted to those imperative for reaching the final product quality, those
intended for process enhancement, or those required to ensure proper operation. As a rule, all chemicals
used have no/low environmental impact upon discharge, and are approved for their intended use by
regulatory agencies.
Based on IDE’s extensive experience in the operation of large-scale desalination plants, an optimal
design for the types and consumption rates of chemicals has been reached. The efficiency of each
process stage in which chemical treatment is necessary has been improved in order to minimize
chemical consumption.
In pre-treatment stages, a flocculation chamber is implemented before gravity filtration for the slow
mixing of a minimal dosage of coagulant following the formation of large and strong flocs that can then
easily be removed by the filtration media6.
The use of antiscalants has been optimized based on actual water chemistry data and long-term trials
performed at existing plants with different products for the optimization of chemical dosing.
Furthermore, innovative approaches are continuously adopted to improve the efficiency of chemical
consumption at the post-treatment stage, with the potential application of the absorption/desorption
processes for the re-use of excess CO2.
3.3.7 Land-based treatment of dual-media filters backwash - Common practice nowadays consists of
land-based treatment of the backwash of dual-media filters to reduce the marine discharge of particulate
matter and residues of process chemicals. The treatment process, designed to achieve removal of ~90%
of the suspended solids retained at the filters, comprises flocculation, sedimentation, thickening and a
final sludge de-watering process. The stabilized sludge (at least 25% dry solids and less than 6%
dissolved solids) is disposed of in an authorized waste disposal site. The clarified water is discharged to
the sea with the brine stream.
The untreated backwash contains particulate matter and heavy metals that occur naturally in the intake
water, iron-hydroxide (Fe(OH)3) flocs formed upon contact of the coagulant with the intake water, and
minute quantities of heavy metals from impurities in the coagulant. At the prevailing pH in the system,
most metals in the backwash will be adsorbed onto particulates and removed by the backwash treatment
process. Considering the envisaged use of coagulants, the efficiency of the backwash treatment and the
dilution ratio of the residual liquid (clarified backwash) with the RO brine stream, iron concentrations in
6
In cases where no flocculation is implemented, large quantities of chemicals are required in order to reach comparative
results.
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the concentrate discharged to the sea do not exceed 0.3 mg/l on a monthly average and 0.5 mg/l at any
given time. This prevents discoloration of the receiving waters (i.e. the potential aesthetic impact
associated with higher concentrations of iron-hydroxide). The level of other heavy metals in the
concentrate is well below international water quality criteria for the protection of marine life [1,2,3].
Consequently, even in the initial mixing zone at sea, metal concentration levels are below those causing
environmental concern.
3.3.8 Use of environmentally-harmless antiscalants - Antiscalants envisaged for use in the facility are
based on Poly-Phosphonate or other suitable substances. Phosphonates are used extensively as antiscaling agents in SWRO facilities worldwide, without regulatory restrictions, as these substances are
considered harmless to the marine environment (being non-toxic to marine organisms at applicable
dosing levels and having low biodegradability rate, typically less than 20% in 30 days). Nevertheless,
use of phosphorus-free or low-phosphorus antiscalants shall be considered, should such substances,
which have been previously proven successful in the RO process as well as harmless to the marine
environment, be available.
3.3.9 Treatment of backwash from limestone reactors - Limestone reactors are backwashed with the
brine of the “polishing” stage. The backwash water is blended with the backwash water from the
pretreatment gravity filters at the sludge treatment unit. This enhances the thickening and neutralization
of the sludge, and prevents peaks of high TSS and turbidity levels in the concentrate discharged to the
sea, which might occur if the backwash from the limestone reactors were to be discharged untreated into
the brine stream.
3.3.10 Use and neutralization of inorganic membrane cleaning solutions - Caustic Soda and
Hydrochloric Acid used for membrane cleaning are neutralized (to produce NaCl) prior to discharge into
the brine stream. No organic chemicals are used for membrane cleaning.
3.3.11 Minimal emissions of greenhouse gases and air pollutants - Emissions of greenhouse gases and
air pollutants are minimized by implementation of the following strategy:

Minimal energy consumption - innovative design approaches, state-of-the-art technologies and
the accumulated experience of other large-scale plants have been combined to reduce the energy
consumption to a minimum. The following main features were implemented: design optimization
and recovery yield of the RO system; optimization of facility hydraulic profile; highest
efficiencies in pumps and motors; introduction of variable-frequency drive devices in critical
stations; major efficiencies at the high-pressure Energy Recovery Device, and implementation of
the Pressure Center and “cascade” concepts.

Use of natural gas as the main source of energy for power generation.

Capture of CO2 from the burning of natural gas and its use for limestone dissolution during the
post–treatment stage is envisaged to be implemented in the future. The technology is based on
capture and purification of CO2 from the burning gas and its direct mixing with permeate water
through an absorber column upstream of the limestone reactors, for the final re-hardening of the
product water.
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REF: IDAWC/TIAN13-012
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3.3.12 Minimal noise emission - The detailed design of the facility and equipment selection assures that
maximum noise levels at sensitive noise receivers does not exceed the limits specified in relevant noise
regulations.
Common mitigation measures with regard to noise emission include:

All machinery is located inside industrial structures with nominal sound reduction of ~27 dB, or
as determined during the detailed design process.

The industrial structures were carefully designed, taking into account ventilation requirements
and all other openings required for normal operation procedures.

Service and access doors provide nominal sound reduction of ~22 dB nominal, as determined
during detailed design process.

Ventilation openings were designed to minimize noise radiation, and silencers are used,
whenever necessary, to ensure that all noise criteria are met.
3.3.13 Prevention and control of chemical leakage and spillage - Management of chemicals (transport
to the site, and storage and handling of chemicals in the facility) is in accordance with the applicable
legislation, taking into account the recommendations of risk assessment for dangerous substances
performed. A defined area at the plant is designated for chemical storage. Storage tanks for corrosive
liquids are placed into secondary containment basins of adequate capacity, lined with anticorrosive
material. In case of any accidental spillage, the liquid will remain within the basin until it is neutralized
and disposed of properly. The Standard Operation Procedures of the facility include specific procedures
for storage, handling, and disposal of chemicals, as well as for incident management including spill
control and clean-up measures.
3.3.14 Solid waste and sanitary sewage collection and disposal - All operational solid waste (used
containers, wastes from routine maintenance works, office waste etc.) is segregated as appropriate,
stored in suitable containers and disposed of in authorized waste disposal sites or sent for recycling, as
feasible.
The sanitary sewerage system is designed and executed according to standards and applicable
regulations. The various branches of the sanitary sewer are connected to a main collector that is
evacuated on a regular basis, or treated by a small compact sewage treatment unit and reused for garden
irrigation.
3.3.15 Landscaping and visual aesthetics - Preservation of the visual characteristics of the natural
landscape in the plant surroundings is of great importance. Accordingly, the following principles were
implemented in the planning of the Facility with regard to landscaping and visual aesthetics:

Minimizing impacts on the natural landscape, as much as possible;

Merging the appearance of buildings with the local landscape;
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
Preserving the natural character of the surrounding landscape;

Rehabilitation of external areas that might be affected by construction works (e.g. grounds used
as temporary organization areas and excess roads) including restoration of the original
topography, as much as possible.
The detailed planning involved relevant experts such as a landscape architect, agronomy consultant, etc.
Specifically, the following elements were implemented:

Water retaining buildings are constructed with smooth concrete surfaces.

Buildings are constructed with the facades based on a combination of steel frames and concrete
sheet templates, and roofs of insulated panels. The concrete sheet templates are painted in colors
that lend the buildings an appearance that blends with the natural view of the local environment.

The maximal height of all plant structures is according to local/regional regulations.

Trees and bushes are planted around and between the buildings to create a strip that conceals the
buildings and blends them with the landscape.
3.4.
Environmental monitoring
After commencement of plant operation, a routine environmental monitoring program will be put in
place in accordance with relevant statutory requirements (e.g. the permit for marine discharge of the
concentrate). The program includes both in-plant monitoring of the intake water and the concentrate
streams and marine environmental monitoring (seawater, sediments and biota). The monitoring program
is designed based on the characteristics of the concentrate and the receiving environment, and takes into
account the results of the Marine Dispersion Model and the background Marine Monitoring Survey.
The results of the monitoring will be used to verify the impact assessments associated with the operation
of the plant and to trigger additional mitigation measures, if necessary.
IV.
FIELD EXPERIENCE [4]
Among the potential adverse environmental impacts of SWRO plants described in the previous sections,
the focal point for concern are the potential impacts on marine ecosystems due to concentrate disposal.
While it is widely suggested that SWRO concentrates have strong potential to have negative impacts on
the marine environment, much of the discussion around this issue is speculative in nature and not based
on actual monitoring of SWRO operations. Especially lacking are results of systematic monitoring of
concentrate discharges from large SWRO plants.
In Israel, three SWRO plants along the Mediterranean coast at Ashkelon, Palmahim and Hadera,
currently produce nearly 300 million m3/year (Mm3/y) of fresh water, equivalent to approximately 20%
of the country’s total potable water resources. Currently, the Hadera and Ashkelon plants are among the
world’s largest operating SWRO plants. In mid-2013, the larger Sorek SWRO plant, now under
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construction, will add 150 Mm3/y of fresh water, and with the construction of two additional facilities it
is expected that by the end of 2013 SWRO will supply 600 Mm3/y.
The Israeli regulatory framework for desalination plants requires baseline, as well as operational,
environmental monitoring related to disposal of the concentrates. Monitoring programs aimed at
assessing the environmental impacts of the concentrates of the Ashkelon, Palmahim and Hadera
desalination plants were implemented shortly after the commissioning stage of each plant, and Sorek’s
plant monitoring program will be implemented this spring, after approval by the regulatory bodies.
The extensive chemical and biological monitoring related to disposal of the concentrates of the
Ashkelon, Palmahim and Hadera SWRO plants provides a wealth of data for scientific assessment of
actual environmental impacts and their spatial extent. This data was examined with respect to a series of
focused questions covering a broad range of potential environmental responses, from effects on water
column processes and sediment quality to effects on benthic organisms.
The phytoplankton biomass has not changed significantly in any of the areas as a result of the SWRO
concentrate discharges, and the discharges certainly did not cause any algal blooms or proliferation of
toxic algae. The levels of heavy metals recorded in the water column in the three areas are much lower
than water quality criteria for the protection of marine life and, therefore, do not represent a risk to
marine organisms. Likewise, the levels of heavy metals recorded in the sediments are lower than
concentrations considered harmful and, therefore, do not represent a risk to benthic organisms.
Coagulant materials do not accumulate in the sediments and thus there is no risk of smothering of sessile
organisms or of ingestion of foreign materials by filter and sediment feeders. Currently, none of the
concentrate discharges constitutes an aesthetic problem. The only negative “environmental response”
that can be attributed to the SWRO concentrates on the basis of the monitoring results, or to the
combined discharges of the concentrates and power plant cooling water at Ashkelon and Hadera, is
changes in the benthic infaunal communities. However, the changes observed are confined to very small
areas (less than 0.2 Km7) near the outfalls and it is highly unlikely that such changes have significant
ecosystem impacts.
The overall conclusion that can be reached from the monitoring results is that the concentrates of the
Ashkelon, Hadera and Palmahim SWRO plants do not have significant adverse impacts on the
ecosystems of the receiving environments. Thus, to date, the Israeli experience demonstrates that with
proper selection of discharge methods and sites, concentrate discharges from large SWRO plants can be
environmentally safe. A similar conclusion has also been observed for the Australian Gold Coast
Seawater Desalination Plant, where results of various monitoring programs indicate minimal impact on
the marine environment [5].
V.
NEW APPROACHES
The primary directions in which desalination solutions can demonstrate environmental responsibility is
through the elimination of the need for chemicals, and therefore for the safe disposal of spent chemicals;
7
The equivalent diameter (D) is: D = 2 * jA/n , where A is the area where the water salinity exceeds the ambient by a
specified percent.
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lowering energy consumption to reduce the CO2 footprint; and minimizing disruption to the landscape
and seascape in the vicinity of the plant.
5.1
Chemical Free Desalination and Lower Energy Consumption
One of the primary uses of chemicals is in the pretreatment process. Typically, pretreatment of raw
seawater uses chemicals such as chlorine, sodium bisulphite, coagulants and flocculants. Today more
resources are being invested in the development of alternate methods of pretreatment including, but not
limited to, methods such as chemical-free, contact flocculation and multimedia gravity filtration
processes. The challenge facing developers is to have these methods able to remove fine suspended
solids and dissolved organic contaminants from the feed water, delivering treated water with a Silt
Density Index (SDI) that complies with the guidelines established by membrane manufacturers for the
safe operation of RO systems.
The chemical-free concept can also be extended to the reverse osmosis (RO) process itself, utilizing
various methods of cleaning that are not based on the use of chemicals. One example of such a method
is the patented Direct Osmosis Cleaning (DOC) process. The concept for the DOC process is to clean
the membranes with pressurized permeate water, a process that requires no plant stoppage, enabling
stable performance and high quality water production even during the cleaning process. This is in sharp
contrast to chemical membrane cleaning processes, which require the shut-down of plant operations for
up to 24 hours at a time, disrupting plant operations and reducing plant availability significantly.
Furthermore, it is expected that the flux of conventional membranes will decrease annually by 7-10%,
requiring higher use of energy to achieve the same level of production.
5.2
Pressure Center Concept – Lower Energy Consumption
One of the keys to increasing the efficiency of a desalination plant is to increase its operating flexibility,
enabling the adjustment of production rates in response to dynamic changes in demand and water
quality. To this end, IDE’s mega desalination plants have implemented a unique Three Pressure Center
design, which separates the operation of the RO membrane segment from the traditional pump –
membrane rack – energy recovery multi-train concept. The feed pumping center itself includes High
Pressure (HP) pumping and Energy Recovery System (ERS) pressure centers. The HP pumping center
supplies the HP feed to the RO banks via common feed lines, and can be optimized by the selection of a
minimal number of large HP pumps working at the highest efficiency rates and best operational
conditions. This model has demonstrated its ability to increase availability and reliability, to deliver
higher efficiencies and flexibility under variable operational modes, to lower the overall energy
consumption and to lower overall CAPEX/OPEX costs.
5.3
Optimization of Membrane Size and Configuration – reduction in plant footprint
A key contributor to the efficiency of IDE’s mega-sized plants is the optimized configuration of the RO
membrane banks. Utilizing a patent-pending design, IDE’s Ashkelon, Hadera and Sorek plants have
implemented a minimal number of independent trains fed by both feed pumping centers. In Sorek, this
design has been enhanced by the implementation of 16” membrane elements installed in vertical
pressure vessels. The behavior of the 16” membrane element, as complemented and confirmed by the
installation and successful continuous operation of vertical 16” pressure vessels in IDE’s Larnaca and
Hadera Plants, is identical to that of the 8” membranes typically used in SWRO plants, resulting in
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identical salt rejection performance and a correspondingly 4.3 times larger flow rate at the same feed
pressure and operation conditions.
The combination of the proven 16” membrane technology installed in vertical pressure vessels results in
an optimized design that enables significantly reduced membrane handling in maintenance operations.
This approach allows a significant reduction in plant footprint, shorter and smaller diameter HP pipes
and an improved membrane loading method. In addition, due to the larger volumes of feed water, this
design reduces membrane fouling and polarization.
VI.
CONCLUSIONS
Most of the potential environmental impacts during construction and operation of desalination facilities
are of a local nature, i.e., of localized spatial extent. The potential environmental impacts during
operation are mostly continuous, while those associated with construction activities are temporary and
mostly reversible.
Specific mitigation measures are presently available and they represent the ‘best available technologies’
with respect to environmental management of desalination facilities, ensuring compliance with the
requirements of the applicable environmental legislation relating to environmental aspects.
Results of various monitoring programs in Israel and Australia clearly indicate minimal impact on the
marine environment resulting from the operation of large scale desalination facilities.
VII.
REFERENCES
1.
The US EPA National Recommended Water Quality Criteria for Marine Waters (2006)
2.
The Australian Water Quality Guidelines for Marine Waters (2000 as amended)
3.
The Recommended Marine Water Quality Standards for the Mediterranean of the Marine and
Coastal Division of the Israeli Ministry of Environmental Protection (2002).
4.
Seawater Desalination and the Environment - the Israeli Experience, Prof. Yuval Cohen, Israel
Desalination Society, 12th Annual Conference, Dec. 2011, Haifa
5.
Impacts of Desalination on the Marine Environment – Some Significant Benefits. Gordon, H.F. et
al., IDA World Congress 2011, Perth, Australia
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